Electronic identification systems typically comprise two devices which are configured to communicate with one another. Preferred configurations of the electronic identification systems are operable to provide such communications via a wireless medium.
One such configuration is described in U.S. patent application Ser. No. 08/705,043, filed Aug. 29, 1996, assigned to the assignee of the present application and incorporated herein by reference. This application discloses the use of a radio frequency (RF) communication system including communication devices. The disclosed communication devices include an interrogator and a transponder, such as a tag or card.
Such communication systems can be used in various identification functions and other applications. The interrogator is configured to output a polling or interrogation signal which may comprise a radio frequency signal including a predefined code. The transponders of such a communication system are operable to transmit an identification signal responsive to receiving an appropriate polling or interrogation signal. More specifically, the appropriate transponders are configured to recognize the predefined code. The transponders receiving the code subsequently output a particular identification signal which is associated with the transmitting transponder. Following transmission of the polling signal, the interrogator is configured to receive identification signals enabling detection of the presence of corresponding transponders.
Such communication systems are useable in identification applications such as inventory or other object monitoring. For example, a remote identification device is attached to an object of interest. Responsive to receiving the appropriate polling signal, the identification device is equipped to output an identification signal. Generating the identification signal identifies the presence or location of the identification device and the article or object attached thereto.
It is preferred in most applications to maximize the communications range of the identification devices. Enabling communications at increased distances or ranges increases the number of applications for which the identification system may be utilized. Further, expanding the range of communications provides robust communications at decreased ranges.